1. Technical Field
This disclosure generally relates to bottles, and more particularly to bottles with improved top loading and lateral stacking resistance.
2. Description of the Related Art
Liquid, flowable and/or sprayable consumer products have been marketed in plastic bottles, such as those made of polyolefins or polyesters. Exemplary bottle materials include polypropylene (PP) and polyethylene terephthalate (PET). While conventionally packaged in non-transparent containers with relatively thick sidewalls, larger quantities (e.g. 500-2000 mL) of heavier products, such as cleaning or detergent liquids, are now capable of being packaged in durable and recyclable plastic bottles with transparent and relatively thinner sidewalls.
Those bottles filled with liquid products often need to be vertically stacked on top of one another, such as during transportation, warehouse storage and/or at point-of-purchase display. The top loading resistance of the bottles required for stacking may depend upon the type of products and the specific stacking configurations. However, conventional plastic bottles generally have limited and insufficient top loading resistance, especially when the products are heavier liquids. As a result, bottles filled with liquid products located at the bottom of a stack may be subjected to substantial top loading forces and may buckle or even collapse, causing economic loss in terms of inventory replacement and the labor needed for clean-up, or damage to the facility or vehicle in which the collapse occurs. In addition to top loading strength, the bottles may require sufficient lateral stacking strength to maintain their structural rigidity, such as during manufacturing, filling, transportation, and/or storage.
Accordingly, efforts have been directed to increasing the top loading and/or lateral stacking resistance of plastic bottles. For example, bottles with a smoothly curved continuous body wall have been found to have good top loading strength. When the body of the bottle includes interconnected walls, it is generally considered desirable to make the transition edge between the walls gradual or “rounded” in order to improve the top load strength of the bottle. Thus, bottles with curved and rounded body profiles are generally considered as having better top loading strength than bottles having more abrupt transitions that may be considered to form relatively “square” profiles.
Bottles with variable wall thickness are also known in the art. For example, it has been found that gradual thickening of the sidewall (up to four times), both upwardly toward the shoulder and neck portions and downwardly toward the bottom base portion, improves bottle strength against laterally imposed stacking and crushing loads, such as in a vending machine. However, the effectiveness of such a wall thickness profile against top loading forces is not known. Moreover, while thickness variation along the longitudinal axis of a bottle may affect the bottle's top loading strength, the effect of latitudinal thickness variation in the bottle remains to be seen.
Finally, bottles constructed with thicker walls and/or more commodity material are generally expected to have greater top loading resistance than bottles with thinner walls and/or less plastic material. Thus, it would be economically and environmentally desirable and unexpected to maintain or even improve the top loading resistance of a bottle while reducing the amount of commodity material used to manufacture it.